1) Field of the Invention
The present invention relates generally to removal of hydrocarbons from subterranean geological formations and more particularly to introducing a material to chemically interact with bicarbonate in the water within the formation producing carbonate scale in the formation interstices, channels and other openings.
2) Description of the Related Art
Waterflooding to increase hydrocarbon production is well known in the art. When a producing well is first drilled, hydrocarbons can be brought to the surface without any enhanced oil recovery techniques such as waterflooding. After a certain period of production, however, hydrocarbons no longer flow into the producing well. To re-establish pressure to produce additional oil, waterflooding can be used.
The waterflood process is injecting water through an injection well. The water displaces hydrocarbons toward a producing well. At the producing well, the hydrocarbons can be pumped to the surface. However the waterflood process causes channelization to occur. The water, instead of flooding the entire subterranean geological formation, forms channels through the formation and goes almost directly from the injection well to the producing well so that the producing well pumps mostly injected water instead of hydrocarbons. Therefore, the well produces small amounts of hydrocarbons and incurs additional expense by pumping excess amounts of water.
To solve the problem of channelization, previous work in the field has sought to form precipitates within underground formations to plug the channels in the formation. U.S. Pat. No. 3,837,400 to Martin for Selective Plugging Process and U.S. Pat. No. 4,024,917 to Martin for Calcium and Magnesium Hydroxide Plugging Process include the disclosure of a method of forming precipitates to plug channels and interstices within a geological formation.
These patents include disclosure of a multi-step process to accomplish such "plugging" as follows: (i) injecting water low in metallic ions; (ii) injecting an aqueous solution of hydroxide into the formation; (iii) injecting water low in metallic ions after the hydroxide solution; and (iv) injecting water high in metallic ions, such as brine or flood water, into the geological formation. During this final step the injection of brine or flood water occurs at a high enough rate to cause thorough mixing of the fluids in the formation which precipitates nearly all of the magnesium hydroxide and other compounds into particulate form. These magnesium hydroxide particulates and other compounds plug channels and interstices in the formation. However this process does not adequately plug the formation because some of the fluid flow paths in the formation are too large to be plugged by particulates. Therefore only a partial plugging, if any, of the formation occurs.